1. Field of the Invention
The present invention relates to methods and apparatus for handling sheets, and in particular to methods and apparatus for inserting sheets into a stream of sheets prior to assembling the sheets into one or more documents.
2. Description of Related Art
With the general increase in quality, speed and capabilities of modern day copiers and printers (generally referred to as document producing apparatus), it has become increasingly desirable to place finishing devices (such as booklet makers) in-line with the document producing apparatus so that human intervention during the document producing process can be reduced. A best case scenario would require users to merely supply the document producing apparatus with blank sheets, initiate the document producing process, and then remove bound booklets from an output tray of the finishing device.
For example, when producing multiple copies of a document such as a booklet, the bypass sheet path of a high speed document producing apparatus such as the Xerox Docutech printer can be placed in communication with an inlet chute of a finishing device such as a booklet maker. The document producing apparatus would then be programmed to produce multiple copies of the document which would be output through the sheet bypass as a continuous stream of sheets. The continuous stream of sheets would contain multiple collated sets of the document. As the sheets enter the booklet maker, the sheets from each set are compiled at an assembly station until one complete copy is contained in the assembly station. When one complete copy of the booklet is contained in the assembly station, the sheets of the booklet are aligned (e.g., by jogging and/or tamping), the booklet is bound (for example, by stapling) and then ejected from the assembly station.
The end-of-set signal which is conventionally output by the document producing apparatus is used by the booklet maker to identify the last sheet of each copy of the booklet so as to initiate the staple/eject cycle.
When the speed at which sheets are output by the document producing apparatus and the speed at which the booklet maker performs its function (e.g., align, bind and eject) are appropriate, it is not necessary to insert skipped pitches between each collated set of the document in the continuous stream of sheets output by the document producing apparatus. That is, as long as the booklet maker can align, staple and eject the booklet before the first sheet of the next copy of the booklet reaches the assembly station of the booklet maker, the document producing apparatus can operate at full speed.
One example involves the use of the above referenced Docutech apparatus in combination with a Signature Booklet Maker (SBM). As is well known in the art, a signature is a sheet having two page images formed on each side thereof. For a more detailed description of signature production, see U.S. Pat. No. 4,727,402 to Smith et al, the disclosure of which is incorporated herein by reference. The signature booklet maker usually includes three modules: the first module compiles the signatures for one booklet into a stack in an assembly station, aligns the compiled signatures, staples the stack along a central binding portion thereof, and then ejects the bound stack into the second module; the second module folds the stapled stack into a booklet; and the third module trims the uneven edge of the folded booklet. Since signature printing is two sided printing (duplex printing), typically on large 11.times.17 inch sheets, the time between each sheet output by Docutech is sufficient for the first module of the SBM (also known as the stitcher) to align, staple and eject a booklet before the first sheet of the next booklet reaches the stitcher. When printing signatures on smaller sheets, where the time between each sheet is less, it may be necessary to insert a skipped pitch between the last sheet of a set and the first sheet of an immediately subsequent set in order to allow the stitcher to perform its functions prior to receipt of the first sheet of the subsequent set. The need for skipped pitches depend on the speed of the document producing apparatus and the speed of the finishing apparatus, and thus is not limited to the above-described example.
Even when using state of the art document producing and finishing apparatus, it may be necessary to insert sheets into the document which are produced by means other than the document producing apparatus, or produced at a separate time from the majority of the sheets contained in the document. For example, it is not uncommon to place specially colored sheet, chapter dividers, photographs or other special sheets into a document. It is generally not desirable or possible to produce these special sheets in the document producing apparatus.
For example, it is common to use preprinted sheets which were produced by four-color offset press techniques as special insert sheets in a document containing mostly text printed on ordinary white paper. In booklets produced from signatures, these special sheets are often used as cover sheets or center sheets containing, for example, coupons. It is not desirable to pass these sheets through the document producing apparatus because the ink on the special sheets tends to be smudged by the paper-handling rollers, etc. of the document producing apparatus.
Accordingly, these special sheets must be inserted into the stream of sheets produced by the document producing apparatus. It is desirable to insert these sheets without disrupting the flow of the continuous stream of sheets. It is also desirable to insert these sheets in a manner which is transparent to the document producing and finishing apparatus so that the operation of these apparatus need not be modified.
U.S. Pat. No. 5,080,340 to Hacknauer et al. discloses a modular finisher apparatus for use with a reproduction apparatus, for forming completely finished reproductions. The finisher apparatus includes a receiver for receiving sheets of sets from the reproduction apparatus. A first feed path extends from the receiver to a sheet collector where received sheets are directed. Collected sheets are stapled into finished reproduction sets. A second feed path extends from the sheet collector to a set collector where finished reproduction sets are collected. The finisher also includes at least one of the following devices: a Z-folder, a saddle stitcher, and an insert tray. Sheet transport paths are provided to any of the included devices.
U.S. Pat. No. 4,602,776 to York et al., assigned to Xerox Corporation, discloses an insertion apparatus for use with a copier and/or a collator for providing on-line and off-line insertion of sheet material or collation, respectively. A supply tray is loaded with one or more types of insert material, each type being separated by a first type of coded sheet. A copying operation is interrupted when a second type of coded sheet, located in the stack to be copied and indicating a location where insert sheets are to be inserted, is detected. As the insert sheets are fed, a second sensor detects the first type of coded sheet (indicating the end of the group of insert sheets), which is then fed to an overflow tray. The normal copying operation is then resumed.
U.S. Pat. No. 4,248,525 to Sterrett discloses an apparatus for producing sets of collated copies wherein some of the sheets in a document (regular sheets) can be reproduced in a collating mode by means of a copier having a recirculating document handler (RDH), while other sheets in the document (insert sheets) cannot be produced in a collating mode by the RDH. Each sheet which cannot be imaged using the RDH is first individually copied multiple times and fed to a separate storage bin. These sheets later will be inserted into the stream of collated regular sheets as they are copied and output from the copier. A controller is preprogrammed with the page numbers of the sheets to be inserted. The regular sized sheets are then placed (in order) in the RDH, and multiple collated copies are made and fed toward a finisher (stapler). Copies of the regular sized sheets in the document are thus output from the copier in order (collated), with the insert sheets missing. Since the controller keeps track of the number of sheets being copied, the controller is able to temporarily stop the RDH at the appropriate time and cause the appropriate insert sheet to be fed from its corresponding storage bin into the stream of regular sheets output from the copier. Thus, collated complete copies of a document are formed.
U.S. Pat. No. 4,961,092 to Rabb et al., assigned to Xerox Corporation, discloses a pre-programmed postcollation system for a copier which uses plural sorter bins and a recirculating document handler. Preprogrammable pause points in the copying operation allow for insertion of a variable number of job inserts or other special copy sheets into the bins being filled (by producing copies of these special documents or by manually inserting them into the bins), repeatably, at any selected document copying point. The copying sequence must be manually restarted after the appropriate insertion operation is completed.